Hydraulic, pneumatic, pneumatic-hydraulic or combined pneumatic-explosion press

ABSTRACT

Press for manufacturing molded or pressed products, comprising a press tool fixed at one end of a moving cylinder. Said moving cylinder is coaxially mounted inside a fixed guiding cylinder fixed and coaxially suspended inside a cylinder forming the outer envelope of the press. The press has a moving wall defining a first variable volume chamber, eight hydraulic jacks with free differential pistons arranged in crown about the central cylinder. The outer envelope comprises a widening provided with at least a bore wherein are arranged explosion means to cause the displacement of the press tool when the press is used as a combined pneumatic/explosion press. The press has reduced overall dimensions, and may be adapted to the manufacture of different articles at various working rates by simple and fast modifications.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Phase corresponding to PCT/CH83/00141filed Dec. 14, 1983 and based upon Swiss National Application 7400/82-4of Dec. 20, 1982.

FIELD OF THE INVENTION

This invention concerns a press which particularly is used for themanufacture of products formed by compacting, sintering, pressing, withthe aid of a mold or by forging, molding surface pressing, or the like.

More specifically this invention relates to a press which is versatileto be used as a hydraulic press, as a pneumatic press, as ahydraulic-pneumatic press or as a combined hydraulic-explosion press.

BACKGROUND OF THE INVENTION

Numerous hydraulic, pneumatic presses are already known. However, thesepresses are generally very space consuming. Furthermore it is necessaryto provide a comparatively expensive and complicated device for theprogramming of these pneumatic or hydraulic presses, if during themanufacture of the product various pressures are desired in succession.

Regarding the use of an explosion press for the finishing of metallicproducts it may, for instance, be noted that these are only mentioned inthe book "Meyers Handbuch uber die Technik" ("Meyers Handbook ofTechnology") published by Bibliographisches Institute Mannheim (page286).

It seems that the main problem of using the press as an explosion pressfor the manufacture of pressed, molded, or forged products is the exactdosing of the quantity of the explosive material or the explosion powernecessary to perform a given degree of work within a short and regulartime interval.

OBJECT OF THE INVENTION

The principal object of this invention is to provide a press which maybe used as a hydraulic press, as a pneumatic press, as ahydraulic-pneumatic press, or as a combined pneumatic-explosion press,which occupies little space and which has an operating cycle which maybe very simply automated. Furthermore with the press according to theinvention, various pressure heads can be achieved during one operatingcycle thanks to a positive control of the pressure exerted on thepressing tool.

These objects are achieved with a press which is particularly used forthe manufacture of products formed with and of a mold by compacting,sintering or pressing, or which serves for the manufacture of, forinstance, metallic products formed by molding, forging, surfacepressing, or the like, and which has a pressing tool fixed at the end ofa moveable cylinder and a device to move this cylinder, and to exert apredetermined pressure on this cylinder and the pressing tool. Accordingto the invention the elements for moving and applying power to thepressing tool are hydraulic, pneumatic, hydraulic-pneumatic or combinedpneumatic-explosion elements.

According to another feature of the invention the moveable cylinder ofthe press is coaxially positioned inside a fixed guiding cylinder, whichis coaxially fixed by suspension inside a cylinder forming an outer wallof the press, whereby this fixed guiding cylinder and the outer-wallcylinder are carried by a supporting platform of the press with theirrespective upper flange ends.

According to another feature of the invention, the central moveablecylinder of the press has a constriction on which rests a moveableseparating wall with an outer cylindrical part which slides sealinglyalong the inner wall of the outer cylinder in order to form a firstchamber of changeable volume filled with a hydraulic medium. Thehydraulic elements for the press can comprise a large number ofhydraulic cylinders which are crown-shaped and positioned around thecentral moveable cylinder in the first chamber of changeable volume andthe moveable separating wall. Each of these hydraulic cylinders has afree differential piston defining an upper and a lower chamber, wherebythe upper chamber of each hydraulic cylinder is fed with a hydraulicpressing element by a pump, and whereby the lower chamber is connectedwith the first chamber of moveable volume regarding the element.

The hydraulic pressure feeding pump feeds the angularly equispacedhydraulic cylinders.

According to another feature of the invention, each hydraulic cylinderhas an extension or an elongation of a reduced cross section, into whichscalingly slides the bar of the free piston of this hydraulic cylinder.This elongation of a reduced inner cross section ends above the pressingtools in order to form a second chamber of a changeable volume, filledwith a hydraulic medium, with the end of the compressing tool for pistonrings.

According to another feature of the invention, the press has anintermediate cylinder positioned around the hydraulic cylinders, and ina coaxial manner inside the outer-wall cylinder, whereby thisintermediate cylinder is fixed with its upper broadening or flange onthe supporting platform of the press, and forms a ring-shaped chambercontaining a coolant with the cylinder forming the outer wall, wherebythe cylindrical part of the moveable wall slides in the inner space ofthis intermediate cylinder.

According to further feature of the invention, the cylinder forming theouter wall of the press has a flange which also extends into the insideof the cylinder, in order to form a container for a cooling medium, suchas water. The intermediate cylinder has a shoulder on this flange and acylindrical part of a smaller cross section, which is in contact withthe part of the hydraulic cylinder forming the elongation or theextension, in order to form in this manner a third chamber of achangeable volume. This third chamber of a changeable volume has anupper chamber formed by the moveable wall, the intermediate cylinder andthe contraction of this cylinder, as well as a lower chamber connectedwith the upper chamber by openings in the constriction of theintermediate cylinder, whereby this lower chamber is formed by theflange of the cylinder forming the outer wall, the part of a less crosssection of the intermediate cylinder and the pressing tool.Advantageously this pressing tool has an upper cylindrical part whichslidingly protrudes into the space between the inner wall of thebroadening of the outer cylinder and the part of reduced cross sectionof the intermediate cylinder.

Furthermore the pressure feeding pump for the hydraulic cylinder has apiston which is fixed on the upper end of the upper part of reducedcross section of the moveable central cylinder of the press and is, forinstance, operated by a screw or spindle press.

According to another feature of the invention, the press has a pistonprovided with a packing, which is slidingly positioned in the centralmoveable cylinder of the press beneath its constriction, and which has apiston rod which is positioned inside the upper part of the reducedcross section of this cylinder, and the cylinder tightly connected withthe piston of the pressure feeding pump. Operating devices for thispiston are connected with the upper part of the piston rod in order toeffect the movement of this rod and of the piston in the centralmoveable cylinder; the operating device can advantageously be formed bya screw press positioned on the screw press for the operation of thepressure feeding pump.

According to another feature of the invention, in case of the use as apress of a combined pneumatic-explosion press, the explosion elementshave at least one cylinder formed by a bore in a broadened part of theregion forming the outer cylinder of the press, whereby this cylinder isprovided with a pipe lining in which a cylinder sealingly slides andwhich is tightly connected with the pressing tool and which forms anoverhang protruding above the upper area of a ring-shaped part of thispressing tool. Devices are provided for the ignition and fuel feeding tothe cylinder. A compressed air feeding device is provided for eachcylinder and, finally, an exhaust pipe is formed on the upper part ofthe cylinder of this explosion element in the broadening of the cylinderforming the outer wall of the press.

The valve faces for the block of the inlet valve, and the block of theoutlet valve are positioned at the upper end of the piston and at theupper region of the cylinder of the explosion elements. Advantageouslythe inlet valve has a longitudinal bore in which coaxially and slidinglythe body of the outlet valve of the cylinder is positioned. The shaft ofthis outlet valve passes the ring-shaped part of the pressing tool, andhas a stop motion device on that part which protrudes the pressing toolin order to effect the opening of the outlet valve after the passing ofa predetermined stroke of the pressing tool, thus limiting the stroke ofthis pressing tool.

Furthermore the compressed air feeding pump for each cylinder is formedwith a fresh air inlet valve provided in an opening at the bottom of thecentral moveable cylinder of the press, whereby the chamber of thecentral moveable cylinder is connected with the chamber of the piston byan air feeding pipe.

Furthermore the pressing tool has a driving piston fixed on the end ofthe central moveable cylinder, on which exchangeable pressing tools arefixed which correspond to the form of the product to be manufactured.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 is an axial section view of the press according to the invention,used as a hydraulic press with the pressing tool located at its upperdead point;

FIG. 2 is a view corresponding to FIG. 1 in which the pressing tool issituated at its lower dead point;

FIG. 3 is a cross sectional view along the line III--III of FIG. 1; and

FIGS. 4, 5 and 6 are axial section views of the lower part of the pressaccording to invention operating as an explosion press and show variousmanufacture phases of a pressed product at the beginning, during and atthe end of the manufacture of this product.

SPECIFIC DESCRIPTION

The press according to invention, illustrated in its totality in FIGS. 1and 2, is positioned on a support by a platform 1. This press may beused individually or combined with other devices which allow a productto be placed below the pressing tool 3 in a mold to manufacture moldedproducts by sintering, pressing, or the like. The molds can betransported in succession by a carousel beneath the pressing tool andguarantee a continuous manufacture of articles. As will be describedbelow, the operating cycle of the press according to the invention, caneasily be automated, and according to the working cycle, a cycle for themanufacture of molded products can be programmed.

The press according to invention, may either operate as a hydraulicpress, as a pneumatic press or as a hydraulic pneumatic press, or as acombined hydraulic-explosion press according to the products to bemanufactured.

In the following, the various operating modes as well as their elementsare described in succession.

With reference to FIGS. 1 to 3 the press according to invention, and inparticular a first embodiment of this press is described; this press mayoperate as a hydraulic, pneumatic or hydraulic-pneumatic press.

This press has an outer cylinder 5 forming the wall of the press andwhich is fixed by suspension at an upper flange 5a on the platform 1 bynuts 68.

The press according to the invention, has also a moveable centralcylinder 2, which is slidingly positioned inside a fixed guidingcylinder 4, coaxially positioned in the inside of a cylinder 5, andfixed with its upper flange 6 on the platform 1 with the help of nuts68. At the lower end of the moveable central cylinder 2 the drivingpiston 64 of the pressing tool 3 is tightly fixed at a flange 2b ofcylinder 2.

This press has also an intermediate cylinder 19 coaxially positioned onthe cylinders 5, 4 and 2, and fixed with its upper flange 20 on theplatform 1 with the help of nuts 68.

The cylinder 5 forming the outer wall, has a first flange 25, which alsoextends into the interior of the cylinder in order to form a ring-shapedcontainer 26 for a cooling medium, such as water. This container has aninner wall 31 provided with a packing 101 in order to guarantee asealing sliding of a cylindrical inner part of the driving piston 64 ofthe press on the inner area of the wall 1. Advantageously the outer wallof the container 26 has a feeding pipe for the cooling liquid (notillustrated).

In the illustrated embodiment, the cylinder 5 of the press has a second,lower flange 69 in order, for instance, to allow the placing of acontainer for a material mixture to be pressed (not illustrated).

The intermediate cylinder 19 has a shoulder 27 and a contraction 28,supported by the flange of the outer wall cylinder 5 with the help of apacking.

The intermediate cylinder 19 consequently defines with cylinder 5 aring-shaped chamber containing a coolant like water, and connected bythe passage 32 in the broadening 25 of the outer cylinder 5. Furthermorethe lower part 22 of reduced cross section of the intermediate cylinder19 is in contact with the inner part of the driving piston 64 of thepressing tool 3 above its total height, and in a sliding manner, and inparticular with the inner area of the cylindrical part 30 of thisdriving piston.

Furthermore the press according to invention, has eight hydrauliccylinders 11a to 11h which are positioned in a crown pattern around themoveable central cylinder 2 and the guiding cylinder 4. The hydrauliccylinders are positioned by suspension with their upper ends in nuts 71ato 71h of openings in the broadening 6 of the guiding cylinder 4.Furthermore these hydraulic cylinders 11a to 11h are kept in theirposition by a fixed lower plate 18 which is welded at the lower end ofthe contracted part 22 of the intermediate cylinder 19, and has openingsfor the lower ends of the cylinders of each hydraulic cylinders 11a to11h.

Each hydraulic cylinder 11a-11h has a free differential piston 12provided with packings 72 and a piston rod 16a-16h which in a sealingmanner slides in the lower elongation area of each hydraulic cylinderwith an inner cross section which mainly corresponds to the crosssection of the piston rod 16. The piston 12 defines at its lower end acylindrical chamber 13 of changeable volume above the moveable plate 8between the intermediate cylinder 19 and the guiding cylinder 4. Thisconnection is made by openings 73 which, for instance, have arectangular cross section and which are formed in the lower area of thecylinder chamber 13 of each hydraulic cylinder 11 underneath the packing72 of the free differential piston 12, when these are at their lowerdead point.

The press has a second chamber of changeable volume 17, 107 which isdefined in the broadening part of each hydraulic cylinder 11a-11h by thelower end of the piston rods 16a-16h as well as of the fixed plate 18.This second chamber of changeable volume has the upper part of thedriving piston 64 of the pressing tool as its bottom.

The press according to invention, has also a third chamber of changeablevolume divided into two chambers, namely an upper chamber 23 underneaththe moveable plate 8 between the moveable cylinder 2 and theintermediate cylinder 19, and a second chamber 24 beneath theconstriction 28 of the intermediate cylinder 19 and between its lowercontracted part 22 and the inner wall 31 of the cooling liquid container26. The two chambers 24, 23 for the cooling liwuid are connected by anopening 29, in the contracted part 28 of the intermediate cylinder 19and which consequently forms the third chamber of changeable volume ofthe press according to invention.

The press has also a central piston 39, provided with packing rings 40which are slidingly arranged in the lower part of the central moveablecylinder 2. This central piston has a piston rod 41 which is slidinglypositioned in the inside of the upper part 2a of a reduced cross sectionof the central cylinder.

In this embodiment the press has a pump 14 for the feeding of ahydraulic element under pressure into the hydraulic cylinders 11a-11hwith the help of an oil distributor which is formed by a plate 15 in theupper broadening 6 of the guiding cylinder 4 and which has a singleopening in order to consecutively divide the hydraulic medium fed underpressure by the pump 14 to each hydraulic cylinder 11a-11h. This platehas a cylindrical part 74 provided with teeth engaging the teeth of adriving wheel 76, carried by an outer cylinder 77 which, with its lowerflange, is fixed at the platform 1 and carries by its upper broadening acase 78 of the feeding pump 14 fixed by nuts 79.

The oil pressure feeding pump 14 has a piston 34 provided with a packing80 which in a sealing manner is slidingly arranged in the inside of thecase 78 in order to form a pressure element chamber 33. The piston 34 issupported on its lower part by a constriction 81 of the upper part ofthe central moveable cylinder 2.

The piston 34 of the oil pressure feeding pump 14 is operated by a lowerscrew press which is included in the case 78 and a pinion 35, which isin contact with a driving wheel 36 and has a screw nut 37 designed forthe upward movement, which is inserted and fixed in a central bore ofthe pinion 35. This screw nut 37 is in contact with a thread shaft 38tightly fixed on the piston 34.

The pinion 35 is carried by lower and upper roller bearings 82, 83.

It is, of course, possible to replace the lower screw press to operatethe feeding pump 14 by another suitable guiding device.

In the preferred embodiment of the invention, the press can have anupper screw press included in an upper case 84 which is fixed with itslower flange 85 at the upper flange 86 of the case 78 by nuts 87. Thiscase 84 carries with its upper flange 88 a cover 89, which is fixed bynuts 90. The upper screw press has a pinion 42 carried by lower andupper roller bearings 91, 92 in contact with a driving gear 43; a screwnut 93 designed for the upward movement is fixed in a central boring ofthe tooth wheel 42, which is in contact with a threaded part of theshaft 41 of the central piston 39 of the press. This piston rod 41traverses the cover 89 and is kept by a guiding yoke 94 with the help ofa nut 95, so that it cannot rotate. This yoke is positioned on at leasttwo guiding slide rails 96a, 96b tightly fixed to the cover 89. Finallythe pressing tool 3 has the driving piston 64, positioned on the centralmoveable piston 2 of the press by a central opening, with a ring-shapedarea 47 at the upper part of which at least one cylinder 46 is fixedforming a piston, the outer area of which is provided with packing rings97 and slidingly positioned in the inside of a pipe 45 in a boring 44,which forms a cylinder in the lower part of the broadening 25 of themoveable outer cylinder 5.

The pressing tool furthermore has a degradable tool plunger 66 fixed onthe driving piston 64 by bolts 98 and nuts 99. The tool plunger 66 has aform conforming with that of the mold of the products to bemanufactured.

The press as described above may operate as a hydraulic press, wherebythe elements forming the hydraulic press are formed by the feeding pump14 for the pressure medium like oil, by the hydraulic cylinders 11a-11h,the first chamber of changeable volume 10, 13, the second chamber ofchangeable volume 17, 107 and by the third chamber of changeable volumeformed by the two chambers 23, 24. The operation of the hydraulic is asfollows:

The lower screw press is operated in order to set under pressure thepressure medium or oil contained in the container or in the chamber 33.

The distributor or bottom 15 is set into rotation in order tosuccessively feed the hydraulic medium into the hydraulic cylinder11a-11h thus effecting the downward movement of the free piston 12a-12h.Advantageously the volume of the container 33 is basically equal to thesum of the volume of each hydraulic cylinder 11a-11h with the pistons12a-12h being at their low dead point. The downward movement of thepiston 34 of the hydraulic feeding pump 14 effects a movement of thecentral cylinder 2 on account of the mechanical power exerted by thepiston 34 on the shoulder 81 of the cylinder 2.

The downward movement of the pistons 12a-12h in the hydraulic cylinder11a-11h pushes the liquid contained in the cylindrical chamber 13 byopenings 73 into the chambers of changeable volume. The pressureincrease of the medium contained in this chamber 10 effects the movementof the moveable plate 8 which consequently exerts a power on the centralpiston 2 at the height of its shoulder or flange 7 and thus on thepressing tool 3.

The downward movement of the pistons 12a-12h at the same time effectsthe downward movement of the piston rod 16a-16hin the chamber ofchangeable volume 17, 107, and consequently causes an increase of thepressure of the hydraulic medium contained in this chamber, and exerts anew pressure on the surface of the driving piston 64 of the pressingtool 3.

Finally the downward movement of the moveable wall 8 effects a pressureincrease in the chamber of changeable volume 23 and forces the hydraulicmedium contained in this chamber to pass through the openings 29a, 29binto the lower chamber in order to exert another pressure on thecylindrical part 30 of the driving piston 64 and thus on the pressingtool 3.

The power of the hydraulic medium exerted consecutively on the head ofeach differential piston 12a-12h, is adjustable by adjusting thepressure produced by the hydraulic pump 14 during the whole downwardmovement of the central moveable cylinder 2 and thus of the pressingtool 3.

As the differential pistons are moving downwards one after another, thepower of the pressure in the first chamber of changeable volume 10 isdetermined in a functional relation between the active surface of thedifferential piston of each hydraulic cylinder and the active surface ofthe wall 8 as well as by the power exerted by the piston 34 of thefeeding pump 14.

Furthermore the volume of the intermediate chamber 23 with the moveableseparation wall 8 at its upper dead point is equal to the volume of thelower chamber 24, with the driving piston 64 being at its lower deadpoint. The power of the pressure exerted by the hydraulic media in thesechambers 23 and 24 is equal to the power of the pressure which hasalready been transmitted by the moveable plate 8 to the driving piston64 with the help of the flange or shoulder 7 of the moveable centralcylinder 2.

Finally the volume of the chamber of changeable volume 107 is equal tothe volume of the chambers 17a-17h of the extensions of the hydrauliccylinders 11a-11h when the driving piston 64 of the pressing tool is atits lower dead point.

During the seccessive downward movements of the differential pistons12a-12h, the power exerted by the oil in chambers 17 and the chamber ofchangeable volume 107 on the driving piston 64 of the pressing tool, isequal to the pressure originating from the relation between the surfaceof a single piston rod 16a-16h and the upper active surface of thebottom of the driving piston of the pressing tool, and depends on thepower produced by the oil feeding pump at the given time.

FIG. 2 shows the position of the various elements of the press with thepressing tool at its lower dead point.

The return of the pressing tool from its upper dead point is effected byoperating the lower screw press in order to push back the piston 34 ofthe feeding pump 14 to its upper dead point and consequently to causethe upward movement of the differential pistons 12a-12h and of thedriving piston 64 to the upper dead point in a synchronous manner withthe upward movement of the piston rod 41 and of the central piston 39with the help of the upper screw press, and by the synchronized rotationof the hydraulic distributor bottom 15. This central piston 39 alwaysremains in its protected position on the lower part of the constrictionof the moveable central cylinder 2. For this purpose the thread shaft 41of the upper screw press or the piston rod is decoupled during thedownward movement of the pressing tool, and again coupled for the upwardmovement of this pressing tool to its upper dead point.

In such a press the packing devices are only provided for the elementssuch as the central piston 39, the differential pistons 12a-12h, theinner wall 31 of the flange 25 of the outer cylinder 5.

With this press according to invention, it is not necessary to providepacking elements between the various chambers of changeable volume 11,13, 23, 24, 17, 107, as the surfaces of the pistons and the moveableseparating wall are calculated in such a way that their relation in allchambers 10, 13, 17, 23, 24, 107 containing a hydraulic with a mainlyequal pressure, is identical.

Consequently these containers themselves may be connected with eachother by small pressure compensation openings which in no way influencethe effectiveness of the press. Furthermore these compensation openingsallow a cut-off of possible differences in volume of the variouschambers originating from faults of fabrication. These compensationopenings therefore allow a filling of the chambers of changeable volumewith a hydraulic medium by a single hydraulic admission opening andparticularly a compensation of possible leakages of the hydraulicmedium.

Consequently the press has the following advantages:

it is able to produce large pressing forces while occupying a smallspace;

the final pressure exerted by the driving piston of the pressing tool isequal to the sum of the various pressures produced in each chamber ofchangeable volume, and results from a multiplication of the pressureexerted by the piston 34 of the hydraulic feeding pump 14;

a significant saving of energy;

a large stroke of the pressing tool compared with the height of thepress, and consequently an important capacity to feed a mixture into themolds as well as a pressing power which is adjustable up to the completepressing or stamping of the parts to be pressed;

this press may be used as a hydraulic press with a very soft operatingmanner, which may easily be automated by programming the pressureexerted by the piston 34 of the hydraulic feeding pump 14, as ahydraulic, pneumatic press or hydraulic-pneumatic press or as a combinedexplosion press as will be described.

It is also very simple to replace the pressing tool and the devices toadjust the pressure and the working cycle of such a press are easilyaccessible.

Therefore the press is easily adaptable in function of the working cycledesired for the manufacture of a special product. This adaptation can,for instance, be effected by:

adjustment of the stroke of the pressing tool,

adjustment of the starting point,

exchange of the tool piston, or

adjustment of the speed of the downward movement and the return movementof the pressing tool.

FIGS. 4, 5 and 6 shown an embodiment in the form of an explosion press,particularly for the manufacture by stamping of metallic products suchas metal sheet 100, which is positioned above a female bottom die 108.

In order to convert the previously described press into an explosionpress, the pistons 46 tightly connected with the ring 47 of the drivingpiston 64 are provided with two valves, namely an inlet valve 48 and adischarge valve 49. A valve face 51 is developed at the the upper end ofthe piston 46, in order to receive the block 52 of the inlet valve 48.Another valve face 53 is provided in the discharging end of a dischargepipe 50 in order to take up the block 54 of the discharge valve 49.

The inlet valve 48 has an axial central bore in which the body 58 of thedischarge valve is slidingly inserted, whereby the shaft 56 of thisdischarge valve is slidingly positioned in a bore 102 forming a valvestem guide, which is formed in the ring-shaped part 47 of the drivingpiston 64. Furthermore the end of this valve shaft 56 is provided with athread, and has a stop element 57, the position of which is adjustableand which is provided underneath the ring-shaped part 47 of the drivingpiston, in order to effect the opening of the discharge valve, after thepressing tool has covered a certain distance, and by this means toadjust the pressing depth of the stamping caused by this press.

The dense chamber 62 of the piston 46 is connected with the chamber ofthe moveable central cylinder 2 by a fresh air admission pipe 63 and isin connection with the combustion chamber 55 when the inlet valve is inits opened position. This combustion chamber is defined between theinlet valve 48 and the discharge valve 49 when these are on theirrespective valve faces.

This combustion chamber is equipped with devices for the fuel injectionand ignition. It goes without saying that the press may have a singlecylinder 44 or several cylinders, for instance three cylinders 44a-44cas shown in FIG. 3.

In this embodiment the tool piston 65 is connected with the drivingpiston 64, has side accessible borings 103 for receiving the piston rod56 and the stop elements 57 and a central boring 104 which on one sideis connected with the atmosphere, and on the other side by a fresh airinlet valve 59 with the chamber of the central moveable cylinder 2. Thisfresh air inlet valve 59 has a valve face 60 which is formed in acircular plate 61, fixed underneath the lower broadening 2b of thecentral cylinder 2. The piston shaft of this valve is positioned in ashaft guide bore in the body of the tool piston 65.

Advantageously in this embodiment the tool piston 65 is formed by theplate 65 which is fixed on the driving piston 64 by boltrs or nuts 98,99, and by a second part 66 fixed by bolts 106 on the plate 65. Thissecond part has a lower area forming the male forging die 67, in orderto effect the stamping of the metallic sheet 100.

The explosion press operates as follows:

The working cycle of such a press is divided into three times:

Inlet of fresh air, compression and explosion exhaust. The fresh airinlet is effected by operation of the upper screw press which permitsthe central piston 39 in the central moveable cylinder 2 to run up toits upper dead point, and by this means effects the opening of the freshair inlet valve 59 and the admission of fresh air into the centralmoveable cylinder 2.

Furthermore the upward movement of the piston 39 and its threaded rod 41effects an upward movement of the pressing tool 3, and consequently ofthe pistons 46a-46c to their respective upper dead points as well as ofthe inlet and outlet valves 48 and 49. The position of the variousmechanical elements during the inlet phase is illustrated in FIG. 4.

As soon as all mechanical elements of the press have reached their upperdead points, the compression phase begins (FIG. 5) by operating theupper screw press, so that now the downward movement of the centralpiston 39 in the moveable central cylinder 2 may be effected. The freshair inlet valve 59 is closed, and the fresh air contained in thecylinder 2 is fed under pressure into the piston chamber 62 by the freshair feeding pipe 63, which causes the opening of the inlet valve 48 andthe closing of the outlet valve 49. The air compressed in the cylinder 2by the piston 39 thereby is fed into the combustion chamber 55. As soonas the pressure in the combustion chamber reaches a predetermined value,which for instance is to be measured by a manometer (not illustrated),the downward movement of the central piston 39 is automatically stopped.The compression phase is now completed.

The fuel thereafter is injected into the combustion chamber 55 andignited by the aforementioned injection and ignition devices, whichcauses the explosion of the gas mixture simultaneously in the threecombustion chambers 55a-55c. This causes the opening of the inlet valves48 and the transmission of the stroke to the pressing tool with the helpof the ring 65, and consequently the stamping of the metal sheet 100.The composition of the gas mixture contained in the combustion chamber,is dosed as a function of the work to be performed and thus the desiredpower of pressing and stamping.

After the pressing tool has executed a predetermined stroke, the ring 65comes into contact with the stop elements 57 positioned on the shaft 56of the outlet valve 49, which causes its opening. By this means theexhaust gas contained in the combustion chamber 55 may escape by theoutlet pipe 50. This position is illustrated in FIG. 6.

Furthermore at this moment the combustion chambers 55a-55c are scavengedby the compressed air in the central cylinder 2 above its piston 59 andin the fresh air feeding pipes 63. Furthermore the cooling of the piston39 is guaranteed by admission and backpressure of the fresh air duringits alternative movement by a channel 105 connected with the fresh airchamber 104.

Advantageously the piston 34 of the hydraulic feeding pump 14 is run upunder pressure to its upper dead point during the first upward movementof the piston 39, and the piston rod 41, or before using the press as anexplosion press, in order to transfer the hydraulic medium containedabove the pistons 12a-12h of the hydraulic cylinder 11a-11h into thecontainer 33 of the feeding pump, for instance by operating the lowerand upper screw press during the fresh air admission into the centralcylinder 2. Thereafter the lower screw press and the oil distributingplate 15 are held in order to prevent the passing of the hydraulicmedium from the container 33 into the hydraulic cylinder 11a-11h.

The hydraulic medium which may have remained in the various chambers ofchangeable volume, and the pistons of the hydraulic cylinder movedownwards or rise upwards, depending on the movements of the centralmoveable cylinder 2 and of the central piston 39 without being exposedto the explosion stroke.

The press according to invention, which may be used as a hydraulicpress, if no fuel is injected into the combustion chamber 55 of thecylinders 44a and 44c, only by setting into motion the lower screw pressand the hydraulic distributing plate 15, is converted to the explosionareas by its blocking and the injection of a fuel into the combustionchamber of the cylinders 44a-44c, which causes the explosion of thisfuel fresh air mixture admitted into this chamber.

I claim:
 1. A press for the shaping of a material, comprising:asupporting platform; an outer fixed cylinder having a flange at an upperend thereof secured to said platform, said outer fixed cylinderdepending from said platform and forming an outer wall of the press; aninner fixed guiding cylinder coaxially received in said outer fixedcylinder with all around clearance and formed with an upper end having aflange secured to said platform; a cover overlying said upper end ofsaid inner fixed guiding cylinder and secured thereto, said cover havinga central opening; a movable cylinder slidably received in and guided bysaid inner fixed guiding cylinder and having a lower end lying below alower end of said inner fixed guiding cylinder, said movable cylinderextending upwardly through said cover; a pressing tool engageable withsaid material mounted on said lower end of said movable cylinder; drivemeans mounted on said platform above said cover and said flanges fordisplacing said movable cylinder downwardly an exerting upon saidmovable cylinder and upon said tool through said movable cylinder apressing force; a central piston slidably received in said movablecylinder and entrainable therewith upon displacement for said movablecylinder by said drive means; and retraction means mounted on saidplatform above said cover and said flanges and adapted to be coupled tosaid central piston for retracting same and thereby entraining saidmovable cylinder upwardly.
 2. The press defined in claim 1 wherein saidlower end of said movable cylinder is formed with a driving pistonhaving a cylindrical part guided in said outer fixed cylinder and asolid ring formed on said cylindrical part, an inwardly extending flangeof said driving piston being connected to an outwardly extending flangeof said movable cylinder and to said pressing tool.
 3. The press definedin claim 2 wherein said driving piston further comprises a ring-shapedpart lying below said solid ring and projecting axially upwardly from aplate fixed to said driving piston and formed with an axial downwardlyprojecting central part bearing on said pressing tool.
 4. The pressdefined in claim 1, further comprising an intermediate cylinder coaxialwith said inner and outer cylinders, said lower end of said movablecylinder being formed with a driving piston carrying said pressing tooland slidably guided on an outer surface of said intermediate cylinder,said intermediate cylinder having an upper end formed with a flangefixed to said platform, said intermediate cylinder and said outercylinder defining between them an annular compartment adapted to receivea coolant, said lower end of said intermediate cylinder being formedwith holes, and a plurality of hydraulic cylinders each received in oneof said holes and extending axially alongside said movable piston whilebeing fixed to said cover and said intermediate cylinder and havingpistons bearing upon said driving piston.
 5. The press defined in claim4 wherein said outer cylinder has a lower end formed with an enlargementdefining a coolant-containing compartment, said intermediate cylinderhaving an outwardly extending shoulder resting on said enlargement. 6.The press defined in claim 4 wherein said movable cylinder is formedwith a shoulder on its exterior defining in said intermediate cylinder avariable-volume chamber closed at an upper end thereof by said cover andcommunicating with the interiors of said hydraulic cylinders, saidhydraulic cylinders being provided with formations engageable with thepistons thereof at the level of said shoulder of said movable cylinder.7. The press defined in claim 6 wherein drive means includes a hydraulicpump having a pump chamber communicating with said hydraulic cylinders.8. The press defined in claim 7 wherein said pump is provided withdistributor means successively communicating said hydraulic cylindersindividually with said pump.
 9. The press defined in claim 8 whereinsaid pump has a pump chamber closed at a bottom side thereof by arotatable bottom member forming said distributor and having a singleopening successively registerable with said hydraulic cylinders.
 10. Thepress defined in claim 6 wherein each of said hydraulic cylinders has areduced cross section at a lower portion thereof in which a respectiverod of the respective piston in the hydraulic cylinder slides, saidpiston rods defining at their lower ends with said driving piston avariable-volume chamber filled with hydraulic fluid.
 11. The pressdefined in claim 6 wherein said driving piston has a cylindrical portiondefining between said intermediate and outer cylinders an annularchamber communicating by openings with the interiors of saidintermediate and outer cylinders.
 12. The press defined in claim 6wherein said drive means includes a pump for feeding a hydraulic mediuminto said hydraulic cylinders under pressure, said pump comprising apump chamber located above said cover and a pump piston fixed on anupper end of said movable cylinder for displacing said medium from saidpump chamber.
 13. The press defined in claim 12 wherein said pump pistonis formed with a screw engageable by a nut having a configuration of adriving gear and meshing with a driving pinion.
 14. The press defined inclaim 6 wherein the volume of said pump chamber is substantially equalto the sum of the volumes of said hydraulic cylinders when the pistonthereof are located at their lowermost positions.
 15. The press definedin claim 12 wherein said retraction means includes a thread on saidcentral piston, a nut engaging said thread and formed with a gear and adrive pinion meshing with said gear.
 16. The press defined in claim 15wherein said drive piston is provided with means disposed above saidretraction means for preventing retention of said central piston. 17.The press defined in claim 1 wherein said outer cylinder is formed at alower end thereof with at least one bore adapted to receive an explosivecomposition for applying explosive force to said tool.
 18. The pressdefined in claim 17 wherein a driving piston is provided to connect saidtool to said movable cylinder, said driving piston being formed with apiston formation engageable in said bore, means being provided forfeeding said bore with fuel and compressed air for igniting a fuel-airmixture in said bore.
 19. The press defined in claim 18 wherein aplurality of such bores and piston formations are provided and saidlower end of said outer cylinder is provided with a coolant chambercommon to all of said bores and said piston formations.
 20. The pressdefined in claim 18 wherein said piston formation is provided with anexhaust valve.
 21. The press defined in claim 20 wherein said exhaustvalve is provided with a rod adapted to actuate said valve after apredetermined stroke of said tool.
 22. The press defined in claim 21wherein said piston formation is provided with an inlet valve having alongitudinal bore in which said outlet valve is slidably and coaxiallypositioned.
 23. The press defined in claim 19, further comprising aninlet valve for feeding air to said bore and provided centrally at thebottom of said movable cylinder.
 24. The press defined in claim 4wherein each of said hydraulic cylinders has a region of reduced crosssection in which a rod of a respective piston sealingly slides, saidregions of reduced cross section terminating above the pressing tool toform a chamber of changeable volume at the end of the respective pistonrod which is filled with a hydraulic fluid.